No Mosfet Fail Configuration and Validation

Hi,

I am using an SBL2360. I am using an output set as "No Mosfet Fail" to control a safety relay. It is not clear to me how this output is supposed to work. If we config it as "Active Low" then the operation is:
a) Low output if all Normal . Goes highZ if Mosfet failure detected

OR

b) Low output when failure detected?

What is the best way to validate this? How can I simulate a failure event to see if the controller responds correctly?

Thanks